TIEE Teaching Issues and Experiments in Ecology - Volume 2, August 2004 EXPERIMENTS Exploring the Lotka-Volterra Competition Model using Two Species of Parasitoid Wasps Christopher W. Beck 1, Judy A. Guinan 2, Lawrence S. Blumer 3, and Robert W. Matthews 4 1 - Emory University, Department of Biology, 1510 Clifton Rd., Atlanta, GA 30322, 404-712-9012 [email protected] 2 - Radford University, Department of Biology, P.O. Box 6931, Radford, VA 24142, 540-831-5222 [email protected] 3 - Morehouse College, Department of Biology, 830 Westview Dr., Atlanta, GA 30314, 404-658-1142, [email protected] parasitic wasps Melittobia digitata (above) and Nasonia vitripennis (below) 4 - University of Georgia, Department of Entomology, on their host Neobellierria pupa Athens, GA 30602, 706-542-2311, © Jorge M. González [email protected] Table of Contents: ABSTRACT AND KEYWORD DESCRIPTORS...........................................................2 SYNOPSIS OF THE EXPERIMENT.............................................................................4 DESCRIPTION OF THE EXPERIMENT Introduction..............................................................................................................7 Materials and Methods......................................................................................…..12 Questions for Further Thought and Discussion......................................................15 References and Links.............................................................................................16 Tools for Assessment of Student Learning Outcomes...........................................18 Tools for Formative Evaluation of This Experiment.........…...................................19 COMMENTS BY CONTRIBUTING AUTHORS...........................................................20 ACKNOWLEDGMENTS, COPYRIGHT, AND DISCLAIMER...................................…39 CITATION: Beck, C. W., J. A. Guinan, L. S. Blumer, R. W. Matthews. August 2004, posting date. Exploring the Lotka-Volterra Competition Model using Two Species of Parasitoid Wasps. Teaching Issues and Experiments in Ecology, Vol. 2: Experiment #1 [online]. http://tiee.ecoed.net/vol/v2/experiments/wasps/abstract.html © 2004 – Christopher W. Beck, Judy A. Guinan, Lawrence S. Blumer, Robert W. Matthews, and the Ecological Society of America. Teaching Issues and Experiments in Ecology, TIEE Volume 2 (tiee.ecoed.net) page 2 Beck, Guinan, Blumer, and Matthews TIEE Volume 2, August 2004 ABSTRACT: In this investigation, students first design experiments to examine intraspecific and interspecific competition using two species of parasitoid wasps. Second, students are guided to a consensus experiment that examines the effect of both types of competition on reproductive output in the parasitoids. Third, the students conduct the consensus experiment in which one or two females are placed on a single host, alone, with conspecific competitors, or with interspecific competitiors. In subsequent labs, students check cultures for emergence of new adults. Six weeks later, students gather data on the number of offspring produced by females under each of the initial densities of founding females. The resulting data are used to estimate the parameters of the Lotka-Volterra competition model. The predictions of the model are then compared to the outcome of interspecific competition treatments. Information is also included on using the appropriate statistical analyses to compare the relative importance of interspecific and intraspecific competition on offspring production. KEYWORD DESCRIPTORS: Principal Ecological Question Addressed: Are What is the relative importance of intraspecific and interspecific competition in two species sharing resources? Does the Lotka-Volterra competition model accurately predict the outcome of competition between two species of parasitoids? Ecological Topic Keywords: intraspecific competition, interspecific competition, resource partitioning, Lotka-Volterra competition model, principle of competitive exclusion, parasitism, parasitoid Science Methodological Skills Developed: hypothesis generation and testing, statistics, graphics, data analysis, quantitative analysis, scientific writing Pedagogical Methods Used: guided inquiry, cooperative learning CLASS TIME: This study requires two 3-hour lab periods and weekly, short observation periods in between. In an initial, 3-hour lab period, students work in groups to design experimental treatments and then are guided to establish experimental cultures. Then, students examine cultures weekly for first emergence of new adults. Cultures are frozen after full emergence, approximately 21 days for Nasonia cultures and 40 days for Melittobia and mixed species cultures. In a second, 3-hour lab period, students count the offspring produced in each experimental culture and then discuss the analysis of the resulting data. OUTSIDE OF CLASS TIME: Students may spend several hours analyzing their data and writing papers based on their results. © 2004 – Christopher W. Beck, Judy A. Guinan, Lawrence S. Blumer, Robert W. Matthews, and the Ecological Society of America. Teaching Issues and Experiments in Ecology, TIEE Volume 2 (tiee.ecoed.net) TIEE EXPERIMENT Exploring Lotka-Volterra Competition Among Parasitoid Wasps page 3 STUDENT PRODUCTS: Students prepare written scientific papers based on the pooled data from the entire class. SETTING: The experiment is carried out entirely in the lab. A field component could be added to have students look for parasitoid wasps in their natural habitats (i.e., mud dauber nests). COURSE CONTEXT: The experiment as described is used in upper-level ecology courses with a maximum of 24 students per lab section. INSTITUTION: The experiment has been implemented successfully at a small private college, a mid-size private university, and a mid-size public university. TRANSFERABILITY: A version of this experiment has been implemented successfully in an introductory biology course for non-majors at a large public university by emphasizing qualitative comparisons of the effects of intraspecific and interspecific competition. The version for introductory biology was presented as a major workshop at the annual meeting of the Association for Biology Laboratory Education (ABLE) and will be published in the proceedings of the conference in June 2005. This version of the exercise does not include examination of the Lotka-Volterra competition model, but involves more qualitative analysis of the results. Prior to publication in the proceedings, the version for introductory biology is available from the authors. The study organisms used in this experiment are used for other activities at the pre-college level. © 2004 – Christopher W. Beck, Judy A. Guinan, Lawrence S. Blumer, Robert W. Matthews, and the Ecological Society of America. Teaching Issues and Experiments in Ecology, TIEE Volume 2 (tiee.ecoed.net) page 4 Beck, Guinan, Blumer, and Matthews TIEE Volume 2, August 2004 SYNOPSIS OF THE LAB ACTIVITY WHAT HAPPENS: In an initial 3-hour lab, students first design experiments to examine intraspecific and interspecific competition using two species of parasitoid wasps. Second, students are guided to a consensus experiment that examines the effect of both types of competition on reproductive output in the parasitoids. Third, the students conduct the consensus experiment in which one or two females are placed on a single host, alone, with conspecific competitors, or with interspecific competitors. Working individually, students set up replicate cultures of the experimental treatments. In subsequent labs, students check cultures for emergence of new adults and record date at first emergence. Cultures are frozen after full emergence, approximately 21 days for Nasonia cultures and 40 days for Melittobia and mixed species cultures. In a final, 3-hour lab, six weeks later, students gather data on the number of offspring produced by females under each condition. The resulting data are used to estimate the parameters of the Lotka- Volterra competition model. The predictions of the model are then compared to the outcome of interspecific competition treatments. LAB OBJECTIVES: At the conclusion of this lab, students will be able to... 1. Describe the life cycle of Nasonia vitripennis and Melittobia digitata, 2. Explain the possible interactions between two parasite species competing for the same host resource, 3. Design an experiment to determine the nature of the interaction between these two species when competing for a common host, 4. Conduct a consensus experiment to determine the effects of intraspecific and interspecific competition on reproductive output in Nasonia vitripennis and Melittobia digitata, 5. Use the resulting data to estimate the parameters of the Lotka-Volterra competition model, 6. Relate class research outcomes to the principle of competition exclusion. © 2004 – Christopher W. Beck, Judy A. Guinan, Lawrence S. Blumer, Robert W. Matthews, and the Ecological Society of America. Teaching Issues and Experiments in Ecology, TIEE Volume 2 (tiee.ecoed.net) TIEE EXPERIMENT Exploring Lotka-Volterra Competition Among Parasitoid Wasps page 5 EQUIPMENT/ LOGISTICS REQUIRED: Equipment/ Logistics Required: Materials for a class of 24 students (working in pairs): • 1 - 2 cultures of Melittobia digitata (WOWBugs) newly emerged adults (Carolina Biological Supply, ER-14-4570, $12.85 for 50-100 wasp late stage pupae), • 2 cultures of Nasonia vitripennis (Jewel wasp) newly emerged adults (Carolina Biological Supply, ER-14-4560,